1. Field of the Invention
The present invention relates to a mobile communication terminal, and in particular to an impedance matching circuit of an RF module of a mobile communication terminal.
2. Description of the Related Art
The term “impedance matching” is intended to include all the measures for reducing reflection caused by a difference in impedance between two different connection terminals when one output terminal and one input terminal are connected with each other. Such impedance matching is used for the purposes of reducing the reflection loss of an antenna in a mobile communication terminal when a wireless signal is output from the antenna when an RF module of the mobile communication terminal transmits or receives a wireless signal.
In general, all RF circuits are provided with characteristic impedance. The characteristic impedance means impedance which is set on the basis of one circuit or system. By setting a characteristic impedance basis, input and output terminals of an RF circuit are made to be compatible with each other. If reference impedance is set for all the RF circuits, reflection loss can be optimized even if special impedance matching is not executed. A mobile communication terminal also requires impedance matching. An impedance matching circuit employed in a mobile communication terminal is also designed in such a manner as to be capable of optimizing reflection loss on the basis of characteristic impedance, which is according to the antenna of the mobile communication terminal.
However, a mobile communication terminal may be subjected to a change in the impedance value of an antenna. For example, if a user inadvertently touches the antenna during telephone conversation, the impedance of the antenna may be increased or reduced due to the influence of the user's body. However, an impedance matching circuit for a conventional mobile communication terminal is only optimized to the preset characteristic impedance of an antenna. As a result, if the impedance of the antenna changes due to the influence of a human body or the like, an RF module for the conventional mobile communication terminal may be subjected to degradation in performance.